Bound plastic books

ABSTRACT

PAGES OF HEAT-SEALABLE MATERIAL SUCH AS THERMOPLASTIC ARE SUPERIMPOSED TO FORM A BINDING EDGE, THE PAGES ARE THEN PLACED IN A HEAT SHIELD WITH ONLY THE BINDING EDGE EXPOSED AND RADIANT HEAT IS APPLIED TO SUCH BINDING EDGE TO BIND THE PAGES TOGETHER.

Feb. 23, 1971 J. F. MCCARTHY Filed Oct. 3,

INVENTOR. JOHN EMCA THY AWORQI United States Patent 3,565,712 BOUNDPLASTIC BOOKS John F. McCarthy, Metuchen, N.J., assignor to UnionCarbide Corporation, a corporation of New York Filed Oct. 3, 1967, Ser.No. 672,597 Int. Cl. 1332b 31/12; B42d 1/00 US. Cl. 15682 1 ClaimABSTRACT OF THE DISCLOSURE Pages of heat-sealable material such asthermoplastic are superimposed to form a binding edge, the pages arethen placed in a heat shield with only the binding edge exposed andradiant heat is applied to such binding edge to bind the pages together.

FIELD OF THE INVENTION This invention relates to binding pages of heatsealable material into publication form particularly binding plasticpages by heat sealing.

THE PRIOR ART With the introduction of the plastic publication such asplastic books there has been initiated a search for improved andsimplified binding techniques over the conventional stitching andglueing methods associated with paper publications. The thermalproperties inherent in thermoplastics have led to heat sealingtechniques as a binding substitute. Thus, it has been propoosed to placea stack of pages between the heating elements, in contact therewith andheat weld the pages together proximate the edges thereof. However, inaddition to the pressure of contact on the pages from the elements therehas been no shielding means to confine the heat to the immediate areadesignated for binding and the heat has spread to the adjacent pageareas with consequent heat distortion problems. It has also beenproposed to fuse plastic pages together by contacting the edges thereofwith a hot plate extending over the whole binding. However, again ispressure disclosed in cooperation with the heating and moreover, it isdiflicult to confine the heat of binding the page edges and extensiveportions of the pages suffer heat distortion. It has also been proposedto bind pages with a strip of heated extruded plastic applied to theedges of the pages. However, this process requires the additional stepsof extrusion and positioning of the strip. Moreover, heat distortion ofpages tends to occur as outlined above. See British patent application647,803 to Schenfield, US. Pat. 2,232,640 to Schwartzman and US. Pat.2,579,488 to Freeman for examples of the above binding methods.

The above methods all have in common the unchecked spread of heat to thepages beyond the binding area itself. Moreover, mechanical pressure isused in conjunction with the heat which tends to thin out the pages orotherwise distort them in the area of binding. Such thinned out areastend to form weak seals and zones susceptible to tearing i.e. a tearonce begun propagates itself along the thinned out strip of the binding.Heretofore the heating sealing method of binding plastic pages or otherpages of heat-sealable material which effectively confined the heatemployed to the binding area and avoided the use of mechanical pressureon the binding area has not been developed.

Accordingly, there has now been discovered a method for bindingheat-sealable pages by heat sealing which is confined to the zone of thebinding. Moreover, a strong binding seal is provided because the use ofmechanical pressure is avoided thus eliminating the tendency of thinning at the cross-section and forming a tear tape contour. The method ofthe invention is particularly suitable for oriented plastic materials aswell as non-oriented plastic materials for readily producingdistortion-free bound books.

SUMMARY Broadly the process of the present invention for binding pagesof heat-sealable materials comprises superimposing pages ofheat-sealable material so as to form a binding edge therefor, insulatingsaid pages from heat except for the binding edge which is exposed andapplying radiant heat to the binding edge to unite the pages in abinding.

By radiant heat is meant heat applied to material without mechanicalcontact by a solid heating element i.e. heat applied by radiation,conduction or convection or a combination thereof. Conduction includesheat conducted from hot gases such as by contacting the binding edgewith a flame.

The invention will become more apparent from the following detailedspecification and drawings in which:

FIG. 1 is an isometric view of a plurality of heatsealable pagespositioned in a support shield embodying the invention in an openposition, and

FIG. 2 is an isometric View of the shield and pages of FIG. 1, theshield being closed.

DESCRIPTION Referring now to the drawings, plurality of pages 20 aredraped over the center plate 14 of support shield 10 as shown in FIG. 1.Shield 10 has, in addition to center plate 14, outside heat shieldplates 12 and 16, the shield plates being hinged and all three platescoming together at base 18 as shown in FIG. 1. After the pages aredraped over the center plate 14, the shield plates 12 and 16 are closedso that only the binding edge 20 of the pages is exposed, as shown inFIG. 2. With the pages being effectively insulated by shield plates 12and 16, binding edge 20 is then exposed to radiant heat from heater 22which unites the pages in a fused binding without mechanical pressurebeing applied as shown in FIG. 2. As indicated by the arrow in FIG. 2the pages and support can be moved e.g. by conveyor belt past theheating source such as heater 22.

By the method of this invention the heat of binding is eflectivelyconfined to the binding area. Moreover, the heat is applied to thebinding edge as radiant heat, e.g. heat provided by a spaced heatingsource or by contact with a flame, without the use of mechanicalpressure which results in a binding that is not thinned in crosssectionnor weakened in a tear-tape contour. Thus, by the method of theinvention the sealable pages, particularly oriented plastic pages, canbe readily bound to produce strong distortion-free seals at the spine ofthe book.

Illustrative of the thermoplastic resins which can be used in thepresent invention are the olefin polymers and the vinyl polymers.Included within the olefin polymers are both the olefin homopolymerresins and the olefin copolymer resins wherein a predominant amount ofpolymerized olefin monomer is present in the copolymer. The olefinmonomers which are particularly useful in preparing such resins are thelower olefin monomers such as ethylene, propylene and butene. Olefinhomopolymers include high and low density polyethylene, polypropyleneand polybutylene, although high density polyethylene is preferred.Olefin copolymers include olefin monomers copolymerized with vinylmonomers. Of particular utility are the ethylene/vinyl copolymers.

Similarly the vinyl polymers included both the vinyl homopolymers andthe vinyl copolymers wherein a predominant amount of polymerized vinylmonomer is present in the copolymer.

Illustrative of vinyl monomers containing the characteristic group, andmixtures thereof which can be homopolymerized or copolymerized to formthermoplastic polymers and which can be utilized in accordance with thepresent invention are the following: vinyl aryls such as styrene,o-methoxystyrene, p-methoxystyrene, m-methoxystyrene, o-nitrostyrene,m-nitrostyrene, omethylstyrene, p-methylstyrene, m-methylstyrene,p-phenylstyrene, o-phenylstyrene, m-phenylstyrene, vinylnapthalene, andthe like; vinyl and vinylidene halides such as vinyl chloride,vinylidene chloride, vinylidene bromide, and the like; vinyl esters suchas vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate,vinyl chloropropionate, vinyl benzoate, vinyl chlorobenzoate, and thelike; acrylic and alphaalkyl acrylic acids, their alkyl esters, theiramides and their nitriles such as acrylic acid, chloroacrylic acid,methacrylic acid, ethacrylic acid, methyl acrylate, ethyl acrylate,butyl acrylate, n-octyl acrylate, Z-ethylhexyl, n-decyl acrylate, methylmethacrylate, butyl methacrylate, methyl ethacrylate, ethyl ethacrylate,acrylamide, N-methyl acrylamide, N,N-di-methylacrylamide, acrylonitrile,chloroacrylonitrile, methacrylonitrile, ethacrylonitrile, and the like;alkyl esters of maleic and fumaric acid such as dimethyl maleate,diethyl maleate, and the like; vinyl alkyl esters and ketones such asvinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether,2-chloroethyl vinyl ether, methyl vinyl ketone, ethyl vinyl ketone,isobutyl vinyl ketone, and the like; also vinyl pyridine, N-vinylcarbazole, N-vinyl pyrrolidine, ethyl methylene malonate and the like,and modified vinyl polymers such as polystyrene modified with rubber,polystyrene modified with hydrocarbon wax, and the like, Copolymers ofthe foregoing monomers are useful in this invention. Such copolymersinclude vinyl chloride/vinyl acetate copolymers; styrene/ acrylonitrile;ethylene/vinyl acetate; ethylene/ethyl acrylate; ethylene/acrylic acid,ethylene methacrylic acid and their alkyl esters and the like; usefulterpolymers are vinyl chloride/vinyl acetate/maleic anhydride,acrylonitrile/ butadiene/styrene, and the like.

Also included among these thermoplastic copolymers are the ionomerswhich are the metal salts of ethylene/ acrylic acid orethylene/methacrylic acid copolymers in which the acrylic acid componentis present in an amount up to about 40% by weight. The metals used informing these salts may be sodium, potassium, iron, magnesium, calcium,copper, and the like.

Also included within this term are the blends of thermoplastic resins.Such resin blends can be tailored to provide desired characteristics.Preferred blends include polyethylene ethylene/vinyl acetate copolymerblends including those defined in copending patent application Ser. No.581,436, filed Sept. 23, 1966 by Jack H. Gardner and ethylene/ethylacrylate copolymer blends and may or may not also include pigments suchas carbon black and titanium dioxide or colored pigments as well asinert fillers such as magnesium carbonate, clays, diatomaceous earth,magnesium oxide, and zinc oxide.

It should be noted that resin compositions formulated for themanufacture of book pages generally contain fillers and pigments toprovide opaque, white or colored surfaces similar to paper. Otheradditives such as stabilizers, plasticizers, and antioxidants,anti-static agents, and the like are also usually present. Suchadditives can and usually are provided in the materials utilized in thepresent invention.

Other thermoplastic resins are also useful in this invention such ascellulose acetate, regenerated cellulose, polycarbonate, linearpolyesters, polyhydroxyether, polysulfone, linear polyamides, rubberhydrochloride, poly- (ethylene oxide), polytetrafiuoroethylene, andsimilar thermoplastic resins which can be formed into films or sheetssuitable for leaves in a book.

Books may be assembled by this invention wherein the successive leavesare not of the same material wherever the resins forming these leavesare mutually compatible in the melt with each other. Thus booklets withsuch bioriented polystyrene interior leaves may be bound together withcovers made of thicker impact modified polystyrenes, pigmented andfilled high density polyethylene thin sheets may be combined with mediumdensity pigmented polyethylene sheet covers; or clear polypropylene filmleaves may be intermixed with pigmented polyethylene leaves;polyhydroxyether films may be combined with polysulfone orpolycarbonates, and so forth.

The method of binding of the present invention may be very etfectivelyapplied to sheets of filled or woven mats or papers, made Wholly or inpart from the fibers made from thermoplastic resins. Such fibers aremade from polyacrylonitrile, linear polyesters, linear polyamides,polypropylene, polyethylene and the like both oriented and unoriented.In addition sheets made from cellulose fibers which have been coatedwith thermoplastic resins such as polyethylene, in which the proportionof cellulose to polymer, may be as high as to 20% respectively. Sheetsof Kraft paper up to .007" mil thick which are coated with films ofpolyethylene or polypropylene of thicknesses as thin as .0075" on bothsides of the paper may be bound by the method of this invention.

The heat sealing characteristics of some of the above mentioned polymersare listed in Table I below.

TABLE I.REPRESENTATIVE HEAT SEALING TEMPER- ATURE RANGES OFTHERMOPLASTIC FILMS AND SHEETS Melting Density point, Heat sealor sp.approx. ing temp. Material gravity F range, F.

Low density polyethylene 0.92-0.92 225 230-400 Med. density p0lyethylenc235 240-400 High density polyethylene 260 260-425 Polypropylene 335335-400 High density PE/EVA/filled 265 270-600 EVA copolymer, 18% VAc206 250-425 EtZhyleEe/ethyl acrylate copolymer, 94 200-250 5 a AEthylene/acrylic acid copolymer, 15%

AA 95 200-250 Ethylene/15% acrylic acid, 35% conve' ed to Na salt .96300-350 Rigid polyvinyl chloride 1. 30 130 200-360 Polyvinyl alcohol 1.21-1. 31 220 320 Polyvinyl fluoride. 1. 38 280 350-400 Polyvinylidinechlor 1. 08 200 280300 Rubber hydrocholnde 1. 11 225 250-350 PlastieizedPVC 1 20-1. 45 180 325-360 Polycarbonate 1. 20 320 420-450Polyhydroxyether 1. 23 220 350-400 Linear polyester (bioriented). 115-1. 39 490 490-500 Polystyrene (bioriented) 1. 0 225 250-325 Impactmodified polystyren 0. 98-1. 10 225 250-325 Cellulose acetate 1. 25-1.35 340 340-450 The thermoplastic pages or leaves of the books of thisinvention can be finished by polishing, scuffing, embossing and by anyof the techniques known to the art to impart a textured finish to thesurface. The leaves can be in the form of film, sheet, foam films, fibermats, and the like. Different types of sheets may be mixed together suchas film for pages and sheets or foamed sheets for covers or inserts.

The support shield can take many forms provided it insulates the majorportion of the pages from the heat that is being employed to bind theexposed portion of the pages. It can be two fiat plates, for example,that are held together with the book pages inside and with the bindingedge portion to be sealed extending a fraction of an inch outside. Itcan be, as a further example, a pair of shields and a center plate whichis simply a frame to hold the pages or to drape the pages over prior toclosing the shields over the pages. The shields and center member canhave the same height in the closed position, but advantageously thecenter member is slightly shorter to reduce the exposed area of thebinding edge portion to a minimum and to discourage formation of anybinding bulge over the top surfaces of the shields. While the shieldsare preferably plates they can also take other shapes and forms such asa pair of blocks which move together to hold the pages i.e. can take asmany and varied forms as do bookends. Moreover, the shields need not besolid but can be apertured at a point removed from the source of heatthat is serving to bind the book. Thus, a pair of shields can be solidin the upper portion and apertured in the lower portion remote from theheat sealing source. Although the heat shields are preferably connectedand hinged as shown in FIGS. 1 and 2 these shields need not be connectedas indicated above but merely pushed together and held in positionduring the heat sealing.

The support shields can be made of various heat resistant materials,conductive, such as metal, particularly aluminum and stainless steel ora non-conductive, for example, asbestos. If the support material isconductive, then the heat employed in sealing the book is readilyconducted away; if the support shield is made of nonconductive materialthen the heat is prevented from reaching the book material significantlybeyond the area of heat binding.

The heat source can be various provided the heating itself is applied tothe portion of the pages to be sealed in a binding. Thus, the heatingsource can be an electric coil, a glass tube, a Micron wire heater andthe like and it can even be an open flame. In a preferred embodiment thebinding edge of the pages is brought in direct contact with a flamewhich flame gives intense heat and thus speeds up the sealing process.

Although the book material is desirably heated to a temperature at or afew degrees above the melting point of the particular material employed,as indicated in Table I, advantageously the material is heated wellabove the melting point short of the temperature that would degrade theplastic material, on brief contact or dwell time, e.g. less than 5seconds, so that each book can be sealed rapidly at production linerates. However, it may be desirable to heat the book material, to besealed, to a temperature within the heat sealing range indicated, forexample, in Table I for a relatively long period of time, as by passingthe pages in a support shield through a long furnace or other heatedzone. However, the longer the time during which the seal is being heatedthe more effective must be the insulating shield; for example a watercooled shield may be necessary. Accordingly, it is preferable to use arelatively short heat binding cycle as by flame as described above orother sources such as a concentrated stream of heated gas including airor a high radiant heating source situated in close proximity with thebinding edge portion of the pages.

The permissible heating time or dwell time of the binding edge of thepages being bound will be determined by the intensity of the heat beingradiated to the binding edge portion and the thermostabilitycharacteristics of the book material. If the material is exposed to heatbelow the degradation temperature of the book material the maximumheating time is determined by the time required for heat to flow fromthe binding edge portion to the adjacent page portions in suflicientquantity to result in heat distortion, commonly more than 20 seconds. Ifthe heat reaching the binding edge is above the degradation temperatureof the book material then the maximum dwell time is usually measured inless than 20 seconds. On the other hand, the minimum dwell time can bemeasured in fractions of a second if the heat applied is within the heatsealing temperature range of the book material or higher.

As previously indicated the limits of the heating cycle are determinedby either moving the book material through a heating zone or moving theheating source with respect to the book material, Preferably the supportshield and enclosed pages with the exposed binding edge are moved, e.g.on a conveyor belt, past one or more heat sources, binding isaccomplished and a book and shield are moved out of the heating zone.

The distance of the heat source to the binding edge portion isdetermined by the thermal characteristics of the book material,intensity of the heat source and the speed or rate at which the bookmaterial and the support shield move with relation to the heating sourcei.e. moves past the source. For example, in one group of trials it wasfound that a book consisting of three-folded predominantly polyethylenesheets draped over a center plate of the apparatus shown for example inFIGS. 1 and 2, were sealed to maximum seal strength in two passes at 18feet per minute, with a one second delay between passes, through a flameabout 4 inch thick and inch long. The following table shows sealstrength against a number of passes at 18 feet per minute.

Although good seals could be produced using the shielding support underradiant and hot air heat, the most efficient heat transfer wasexperienced as indicated in the above table, using a forced naturalgas-air flame. In another group of trials, book bindings 9 and 11 incheslong, respectively, were sealed moving at a rate of ft./min. through ahorizontal gas-air flame which was about 8 inches long and about A inchthick. Much faster linear rates are anticipated with the use of manyburners along the path of travel.

Draw-on covers can be attached by coating the backbone i.e. the spine orbinding edge of the book with a fusible hot melt adhesive whose meltingpoint is lower than the heat distortion temperature of a cover material.The coveris brought in contact with the back-bone and is heated by a hotplaten so as to fuse the hot-melt adhesive through the cover materialand cause the cover to adhere to the back-bone. Especially effective forbooks made of polyethylene sheets is a hot melt consisting of lowmolecular weight ethylene/vinyl acetate copolymer and a tackifier suchas rosin or a phenolic resin and a petroleum wax.

The following example is illustrative of the present invention and isnot intended to limit the same. All parts in percentages are by weightunless otherwise specified.

EXAMPLE 1 A support shield was utilized to concentrate heat of bindingonly at the intended area of seal of several pages as described below.The support shield consisted of two pieces of two inch aluminum anglefor a base and three plates. The center support plate was galvanizedsheet metal .030 inch thick. The outer two shield plates were .063 inchthick aluminum mounted to the base by hinges. When the support shieldwas closed all three of the plates presented their top edges at the samelevel. With the support shield in the open position as indicated in FIG.1, three folded layers of .005 inch predominantly polyethylene sheetwere draped over the center plate. The two aluminum shield plates wereswung upward enclosing and protecting all areas but the exposed spine orbinding edge of the pages as shown in FIG. 2. A conveyor served totransport the support shield, enclosed about the pages, at constantspeeds under the flame supplied by a Fisher natural gas-air multi-fiameburner. Because only one burner was used the speed of the conveyor wasset to 18 feet per minute, a speed that allowed the support shield to beplaced and removed from the conveyor while in motion. Good seals wereproduced with two passes at 18 feet per minute with one second delaybetween passes. Good seals were also produced with radiant heat andforced hot air. The fastest or most eflicient heat transfer, allowingthe book continuous movement, was experienced for a forced air-gas flameabout inch thick, with the flame contacting the binding edge. It wasclear that increased flame area would allow for increased conveyorrates. The book thus sealed exhibited superior seal of strength, noobservable distortion to any of the pages nor thinning of thecross-sectional thickness of the sealed area, since no mechanicalsealing pressure was used, providing a strong tear resistant seal.

What is claimed is:

1. A method for bookbinding a plurality of heat-sealable sheets ofthermoplastic resin material which comprises;

(a) folding said sheets on a suport shield,

(b) cooperatively holding said folded sheets in place on said supportshield by means of two outer heat shield plates, while allowing only thefolded edge to be exposed, and

(c) heating the exposed folded edge and all underlying folded edges ofsaid plurality of folded sheets by means of radiant heat, andsimultaneously fusing only References Cited UNITED STATES PATENTS1,858,685 5/1932 Semon 28121 2,066,620 1/1937 Grammer 28115 2,232,0622/1941 Gurwick 9335 2,232,640 2/ 1941 Schwartzman 9335 2,488,212 11/1949Lloyd, Jr. 156--306X 2,562,146 7/1951 Hultkrans 9335UX 2,679,194 '5/1954Ehrenfried et a1. 93-35X 3,093,396 6/1963 Segreto 281-21 3,075,8681/1963 Long 15682 FOREIGN PATENTS 647,803 12/1950 Great Britain 156-272BENJAMIN R. PADGETT, Primary Examiner H. E. BEHREND, Assistant ExaminerUS. Cl. X.R. 156272; 28121

